Are you a professional webmaster? Or perhaps you are just learning HTML?

Do you agree that the best way to increase your skill is learning how other sites are made?
To see what's under the hood of those sites, you must view their HTML code.
You say: "True, but I can select View source command in my browser". Right, but View Source is very inconvenient for learning HTML. Why? Because: Web Browser (we will talk about Internet Explorer only) shows not the same HTML source as you see! It shows HTML that was loaded from the server without any further processing.
However, modern sites extensively use Dynamic HTML for changing the page code after loading. Hence, what-you-see is NOT what-you-get! Usually, you want to analyze only the code of a certain part of the page, not the entire page. The time needed to find the right code block may be significant. Every time you must select View Source command from the menu and switch to the text editor. Instant Source will resolve these problems. It integrates into Internet Explorer, so you don't need to use an external viewer.

Features: Quick access. Click on the button on the Internet Explorer toolbar to invoke Instant Source.
You get the HTML of the page element as quickly as possible - just hover a mouse over it, or select it.
Instant Source displays the HTML code that exactly matches the visible content of the page.